01 -
Start preheating the oven to 350°F. Beat together the softened butter and sugar until fluffy and light. Stir in the egg, powdered sugar, oil, and vanilla. Mix the flour, cream of tartar, and baking soda in a separate bowl, then fold that into the butter mixture until fully combined.
02 -
Scoop out one medium ball and a smaller ball of dough for each well in the muffin top pan. Dip the bottom of a glass in sugar and press each dough ball flat to form a well.
03 -
Let cookies bake in the oven for 8–10 minutes. They're done when the edges firm up. Let them cool briefly in the pan and then move them to a rack to cool completely.
04 -
Whisk together the pudding mix and milk until it's thickened. Gently blend in the Cool Whip, then use about 2 tablespoons to fill the center of each cookie.
05 -
Heat the cream and chocolate in the microwave in 30-second bursts, stirring each time, until smooth. Use a tablespoon to add a layer of ganache on top of each cookie.